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fast-uri vulnerable to path traversal via percent-encoded dot segments

CVSS 3.1 7.5 HIGHEUVD CVSS 3.1 7.5 CVSS 3.1 · ce714d77-add3-4f53-aff5-83d477b104bb · Secondary 7.5 HIGHCVSS 3.1 · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c · Secondary 7.5 HIGHCVSS_V3 Publisher rating HIGHFixed by fast-uri 3.1.1Fixed by fast-uri 2.4.1KEV status unknown

cve-program · CVE-2026-6321

Published

fast-uri decoded percent-encoded path separators and dot segments before applying dot-segment removal in its normalize() and equal() functions. Encoded path data was treated like real slashes and parent-directory references, so distinct URIs could collapse onto the same normalized path. Applications that normalize or compare attacker-controlled URLs to enforce path-based policy can be bypassed, with a path that appears confined under an allowed prefix normalizing to a different location. Versions <= 3.1.0 are affected. Update to 3.1.1 or later.

Read the publisher's advisory

euvd · EUVD-2026-27129

Published

fast-uri decoded percent-encoded path separators and dot segments before applying dot-segment removal in its normalize() and equal() functions. Encoded path data was treated like real slashes and parent-directory references, so distinct URIs could collapse onto the same normalized path. Applications that normalize or compare attacker-controlled URLs to enforce path-based policy can be bypassed, with a path that appears confined under an allowed prefix normalizing to a different location. Versions <= 3.1.0 are affected. Update to 3.1.1 or later.

Read the publisher's advisory

nvd · CVE-2026-6321

Published

fast-uri decoded percent-encoded path separators and dot segments before applying dot-segment removal in its normalize() and equal() functions. Encoded path data was treated like real slashes and parent-directory references, so distinct URIs could collapse onto the same normalized path. Applications that normalize or compare attacker-controlled URLs to enforce path-based policy can be bypassed, with a path that appears confined under an allowed prefix normalizing to a different location. Versions <= 3.1.0 are affected. Update to 3.1.1 or later.

Read the publisher's advisory

osv · GHSA-q3j6-qgpj-74h6

Published

### Impact `fast-uri` v3.1.0 and earlier decodes percent-encoded path separators (`%2F`) and dot segments (`%2E`) before applying dot-segment removal in `normalize()` and `equal()`. This makes encoded path data behave like real `/` and `..`, so distinct URIs collapse onto the same normalized path. For example, `http://example.com/public/%2e%2e/admin` normalizes to `http://example.com/admin`, and `equal()` considers them the same URI. Applications that normalize or compare attacker-controlled URLs to enforce path-based policy can be bypassed. A path that looks confined under an allowed prefix can normalize to a different location. ### Patches Upgrade to `fast-uri` >= 3.1.1, or if you are in the v2.x release line, v2.4.1 ### Workarounds None. Upgrade to the patched version.

Read the publisher's advisory

Affected versions, risk and source history

Related advisories and sources

Publishers link these advisories through the identifiers shown below. A shared identifier or date alone does not tell you whether your software is affected or whether the advisories describe the same cause.

CVE-2026-6321 · CVE overview and exploitation status

EUVD-2026-27129

GHSA-q3j6-qgpj-74h6

cve-program · CVE-2026-6321

euvd · EUVD-2026-27129

nvd · CVE-2026-6321

osv · GHSA-q3j6-qgpj-74h6

Related changes

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